Many implantable medical devices require electrical systems to power the implant. Typically, this is achieved using percutaneous wiring to connect a power source to the implant.
More recently, there has been development into powering an implanted device wirelessly with a Transcutaneous Energy Transfer (TET) system, e.g., through an oscillating magnetic field. For a TET system to be useful, electrical energy storage and processing must be provided when external power is interrupted or not available. This electrical energy processing and storage can be implemented with solid-state electronics and a battery.
Typically, implantable medical devices, such as implanted sensors, require very little power to operate. With such low power levels (on the order of milliwatts), power transfer levels and efficiency can be lower. With higher power devices (e.g., on the order of watts and up to 15 W or more), efficient transfer of wireless power is extremely important. Additionally, positions within the body are limited that can accommodate larger implanted devices, some of which are deep below the skin surface. These implant locations require additional attention to position and orientation of both the transmit and receive coils, as well as techniques to improve and maximize transfer efficiency.
Previous TET systems for implantable medical devices required the implanted receiver coil to be positioned just under the skin, and typically include a mechanical feature to align the receive and transmit coils and keep them together. By implanting these devices directly under the skin, the size and power requirements of these implanted devices is limited if they are to be powered by a TET system.
Conventional wireless power transfer systems typically use rigid coils to both transfer and receive wireless power. A rigid coil has the advantage of being easy to manufacture and not placing stress on the wire used in the coil. However, rigid coils cannot be contoured to the shape of a patient, and can therefore be uncomfortable for patients to wear and use.